Photovoltaic power generation is becoming widespread as a measure to counter global warming. Meanwhile, there has been a trend in recent years to curb power sales prices of photovoltaic power generation. This requires photovoltaic power generation facilities that are at a low cost and generate much electric power. The amount of power generation is affected not only by the conversion efficiency of photovoltaic panels but also by the installation angle (inclination angle and azimuth angle) and the installation position of each photovoltaic panel. Specifically, the elevation angle (altitude) and the azimuth angle of the sun vary depending on the time and the season, and the amount of solar radiation received by photovoltaic panels thus varies depending on the installation angle of each photovoltaic panel, thereby increasing or decreasing the amount of power generation. Tracking mounts have been known that are configured so that photovoltaic panels track the sun in response to changes in the elevation angle and the azimuth angle of the sun. Such tracking mounts are high in cost.
To increase the amount of power generation from fixed photovoltaic panels, design of the installation angle and the installation position is important. Conventionally, it is recommended that the azimuth angle of photovoltaic panels be due south in general. It is also recommended that the inclination angle of the photovoltaic panels be 5 to 40 degrees (an elevation angle of 85 to 50 degrees). The inclination angle of each photovoltaic panel is designed taking into account not only differences in elevation angle and azimuth angle of the sun due to differences in longitude and latitude of photovoltaic power generation facilities, but also the photovoltaic panels' mutual effect of shadows, the accumulation of snow or dust, and the strength of mounts against the wind, for example. More specifically, a single photovoltaic panel tends to receive more solar radiation in a case in which the inclination angle of photovoltaic panels is high (30 degrees (an elevation angle of 60 degrees), as an example) than in a case in which the inclination angle thereof is low (10 degrees (an elevation angle of 80 degrees), as an example), on average. The case in which the inclination angle is high also has the advantage of snow or dust being hard to accumulate. At the same time, photovoltaic panels cast shadows over other adjacent photovoltaic panels more easily in the case in which the inclination angle of the photovoltaic panels is high than in the case in which the inclination angle thereof is low. Two adjacent photovoltaic panels thus need to be widely spaced from each other. As a result, fewer photovoltaic panels may be installed, so that the amount of power generation ends up being decreased. Additionally, photovoltaic panels are more susceptible to the wind in the case in which the inclination angle of the photovoltaic panels is high than in the case in which the inclination angle thereof is low, which sometimes requires strong mounts and may be a factor in increasing the cost.
The amount of photovoltaic power generation is greatly affected by weather conditions. For example, photovoltaic panels receive less solar radiation when it is cloudy or rainy than when it is sunny. The conversion efficiency of photovoltaic panels tends to decrease as the air temperature is higher. Because power poles are often installed for photovoltaic power generation facilities, the power poles cast shadows over the photovoltaic panels, thereby decreasing the amount of power generation. In more recent years, fewer sites have been available that are sufficiently wide and flat and suitable for photovoltaic power generation facilities. Consequently, there is a need to install photovoltaic power generation facilities in relatively small sites, sites having irregular shapes, inclined sites such as intermontane regions, or undulating sites. In such a case, buildings such as warehouses, trees, and mountains around the photovoltaic power generation facilities, or undulations in the sites, for example, may cast shadows over photovoltaic panels, and become a factor in decreasing the amount of power generation. The shapes of the sites may limit the azimuth angle and the installation position of photovoltaic panels. For example, the azimuth angle of all or part of photovoltaic panels in a photovoltaic power generation facility is not due south in some cases. As described above, the amount of photovoltaic power generation depends on various natural conditions, siting conditions, and other conditions. Therefore, it is not easy to determine the optimum installation angle and installation position of photovoltaic panels.
To address the problem, a method has been known by which to calculate the amount of power generation by changing condition settings for the installation angle of photovoltaic panels and the incident amount of sunlight for each season or each time slot, and calculate annual power purchase cost on the basis of the calculated amount of power generation, and determine the installation angle of each photovoltaic panel on the basis of the calculated power purchase cost (see Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2017-174175). Patent Literature 1 also discloses that the incident amount of sunlight is calculated taking into account the installation position at a point where a photovoltaic panel is installed, positional information including environmental information regarding the surrounding environment serving as a light shield, and the rate of fine weather, and that the amount of power generation is calculated. According to the method of Patent Literature 1, the installation angle of each photovoltaic panel is determined to reflect not only changes in the elevation angle and the azimuth angle of the sun but also some effect of weather conditions and the surrounding environment that casts shadows over the photovoltaic panels.
Mounting equipment, such as a mount, is used to install photovoltaic panels in a site at an installation angle thus designed. Even if the ground of the site is not flat, photovoltaic panels are installed at an installation angle as designed, by adjusting the height of the foundation or the length of the feet of the mount. In undulating sites or inclined sites such as intermontane regions, however, it may be difficult to install photovoltaic panels at an installation angle as designed even if the height of the foundation or the length of the feet of the mount are adjusted. In such a case, sites are developed. Although sites that are inclined but have flat slopes sometimes do not need developing, when the inclination angle of slopes is significantly high or when slopes face a direction significantly away from the south, sites may be developed. Through development, a ground that is uniformly level and flat is sometimes formed, and a plurality of flat grounds that are stepwise are formed other times. An inclined ground of which surface is flat is also formed in some cases.
Meanwhile, development increases the cost of photovoltaic power generation facilities. Even if development enables photovoltaic panels to be installed at an installation angle as designed and the maximum amount of power generation to be achieved, the cost of development may worsen profits contrarily. Thus, the cost of development as well as the amount of power generation need to be considered. To address the problem, a method has been known to acquire geographic data on a site via the Internet, estimate an undulation state of the site on the basis of the geographic data, regard the height intermediate between the highest portion of a convex part and the lowest portion of a concave part that are adjacent to each other as a datum line after development, calculate the amount of earth cutting and the amount of earth filling to level the site along the datum line, and calculate the cost of development from the amount of earth cutting and the amount of earth filling (see Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2017-045163).